In our British Patent Specification No. 1601918 it is mentioned that between the years 1880 and 1900 there were various proposed forms of compressed air powered ammunition for use in a suitable weapon for shooting, without some of the cost and other disadvantages inherent in using firearms; but such proposals were unsuccessful for various reasons, and the idea seems to have been abandoned for a long time. In fact, in Swiss Pat. No. 16072 granted in 1898 to Dr. J. Meuli-Hilty there was proposed a form of cartridge of a king (hereinafter referred to as "said kind") which comprised a hollow pressure casing having an internal gas storage space, a rear passage leading rearwards from the storage space, a front passage extending forwards from the storage space, and a movable member having a normal position in which it prevents gas flowing from said storage space, which movable member is movable forwards to allow gas to flow from said storage space.
However, the front and rear passages were provided in spaced apart stuffing boxes secured in the casing, and the movable member was in the form of a hollow tube co-axial with the casing. The tube extended through the stuffing boxes and was provded with two ports spaced apart so as to be closed by the stuffing boxes when the tube was in the normal position. The tube had one end portion closed by a valve, which end portion was exposed at a rear end of the cartridge, and had a front end portion which terminated within a front part of the casing to the rear of a bullet seated in a front end of the casing. A spring urged the tube rearwards to bring a stop on the front end position of the tube into contact with a front one of the two stuffing boxes. The storage space between the stuffing boxes could be charged with compressed gas by removing a nut from a rear end of the tube, opening the valve, and rotating the tube to bring a rear one of the ports into alignment with a radial opening in the rear stuffing box. Thereafter, the valve was closed, the nut was replaced. The cartridge was discharged by driving the tube forwrds towards the bullet, thereby bringing the front port to a small space between the bullet and the front stuffing box, and thereby allowing gas to escape from the large space to the small space via a restricted path comprising the radial opening, the rear port, the interior of the tube and the front port. At all times the tube occupied the front and rear passages and was engaged by the stuffing boxes to seal these passages.
This proposed form of cartridge does not appear to have been successful, and the proposal does not appear to have given rise to any subsequent developments, possibly because of the disadvantages inherent in the cartridge, in particular:
(a) the discharge path provides a severe restriction upon the rate of gas discharge, whereas a rapid discharge is necessary; PA1 (b) the stuffing boxes used to cover the ports and seal the passages would not have been effective to retain gas at the high pressure required for long periods, and any attempt to provide effective seals would have given rise to considerable frictional resistance to movement of the tube, unless the latter had a very small diameter; and PA1 (c) the procedure for charging the cartridge was complicated and required an externally accessible manually operable stop-cock form of value. PA1 (d) are complex, PA1 (e) have to be constructed with great precision, PA1 (f) are expensive, and PA1 (g) incur a slight delay due to the sequential operation of the parts constituting the servo-mechanism culminating in the rearwards (towards the base) movement of the piston, before the discharge valve means is opened. PA1 (a) the movable member is a movable valve member, PA1 (b) the movable valve member is movable bodily forwards from said normal position to allow gas to escape from the storage space directly through both of said passages. PA1 (a) to open the actuation passage to allow gas to escape rearwards from the pressure casing, and PA1 (b) to drive the plug forwards out of said throat to allow compressed gas to escape forwards from said pressure casing directly through said throat. PA1 (a) locating the cartridge in a charging chamber, PA1 (b) abutting the movbale valve member or a missile to which the movable member is appended to hold the valve member substantially in or closely adjacent to the normal position, and PA1 (c) pressurizing the charging chamber, whereby to displace the resilient sealing member or members, e.g. sealing ring or rings, to allow the cartridge to be pressurized without moving the movable valve member out of the passages.
In our British Patent Specification No. 2124346A there are disclosed rechargeable cartridges which have some similiarity with that disclosed in Swiss Pat. No. 16072 of 1898, in that the cartridges are generally of said kind. However, the cartridge disclosed in said Specification No. 2124346A are of a servo operated form in which the cartridge comprises discharge valve means to close the front passage (which valve means is openable by a first force for forwards discharge of said gas to propel a missile): a servo-mechanism adapted to utilize energy from the stored gas to provide said first force; and servo actuating means actuable by a second force smaller than said first force.
In these two operated cartridges, the servo mechanism comprises a piston alongside the rear passage, and the movable member forms part of the servo actuating means. The movable member is movable forwards from the normal position to cause gas to be discharged rearwards from the storage space via said rear passage to expose the piston to said opposed unequal thrusts, one of which thrusts is provided by gas stored under pressure in the casing. The piston is movable by said unequal thrusts to move the discharge valve means forcibly rearwards to allow gas to escape from said gas storage space directly forwards through the front passage to propel a missile.
The piston thus utilizes energy from compressed gas stored in the casing to provide power for opening the discharge valve means, for rapid forwards discharge of the compressed gas.
The servo operated cartridge has the advantage that initial actuation of the actuating means is not substantially resisted by the gas pressure in the storage space, but unlike the cartridge shown in said Swiss Pat. No. 10672 and our aforesaid British Pat. No. 1601918, has the major advantages that the initial actuation only requires a small actuating force to be applied to the movable member of the actuating means, and that initial actuation enables the stored gas pressure to be utilizes by the integral servo-mechanism which acts rapidly and automatically to provide the large force required to open the discharge valve means.
However, the servo-operated cartridges have the disadvantages in that they:
What is needed is a cartridge which can be constructed so as to be used in known small arms as a substitute for explosive (chemical) cartridges, while avoiding or reducing the problems mentioned hereinbefore and, in particular, the aforementioned disadvantages (a) to (g).
The present invention has some similiarity with the disclosed in Swiss Pat. No. 16072 or 1898 in that is is of said kind.